Transcatheter heart valve with micro-anchors

ABSTRACT

Various embodiments of methods and apparatus for treating defective heart valve are disclosed herein. In one exemplary embodiment, a transcatheter heart valve is disclosed that includes an expandable shape memory stent and a valve member supported by the stent. A plurality of micro-anchors can be disposed along an outer surface of the stent for engaging native tissue. The transcatheter heart valve can be configured to be advanced into a dilated valve annulus via a balloon catheter. The balloon can be inflated to expand the transcatheter heart valve from a collapsed diameter to an over-expanded diameter such that the micro-anchors engage tissue along the surrounding valve annulus. After engaging the tissue, the balloon can be deflated and the shape memory stent can retract or recoil toward its predetermined recoil diameter. As the stent recoils, the surrounding tissue is pulled inward by the stent such that the diameter of the valve annulus is reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 60/980,112, filed Oct. 15, 2007, which is incorporatedherein by reference.

FIELD

The disclosed technology relates generally to methods and devices forimproving valve function of a heart. For instance, embodiments of thedisclosed technology can be used to treat aortic insufficiency in ahuman heart.

BACKGROUND

The aortic valve in the human heart is a one-way valve that separatesthe left ventricle from the aorta. The aorta is a large artery thatcarries oxygen-rich blood out of the left ventricle to the rest of thebody. Aortic insufficiency is a condition in which the aortic valve doesnot fully close during ventricular diastole, thereby allowing blood toflow backward from the aorta into the left ventricle. This leakage ofblood through the aortic valve back into the left ventricle is oftenreferred to as aortic valve regurgitation.

Aortic insufficiency is typically caused by aortic root dilatation(annuloaortic ectasia), which is idiopathic in over 80% of the cases.Aortic insufficiency may also result from other factors, such as agingand hypertension. In any case, the regurgitation of blood resulting fromaortic insufficiency substantially reduces the pumping efficiency of theleft ventricle. Therefore, even during periods of rest, the heart mustwork hard simply to maintain adequate circulation through the body. Overtime, this continuous strain on the heart can damage the left ventricle.For example, the additional strain on the heart may result in athickening of the heart muscle (hypertrophy). When heart-wall thickeningoccurs due to aortic insufficiency, the geometry of the heart can beadversely affected and the heart can be permanently damaged.

Although aortic insufficiency is relatively common, the treatment ofthis condition still represents a substantial clinical challenge forsurgeons and cardiologists. For example, because aortic insufficiencyhas a long latency period, afflicted patients may already be atsignificant risk for heart failure by the time the symptoms arise. Inmany cases, when patients are not monitored well for aorticinsufficiency and are left untreated, the patient's left ventricle maybecome irreversibly damaged before therapy can be delivered. Therefore,even if a defective aortic valve is replaced with a prosthetic valve,the patient may never fully recover and their survival rate may besubstantially impaired.

Existing methods of treating aortic insufficiency suffer from a numberof significant disadvantages. For example, open heart surgical valvereplacement is often too traumatic for older and/or frail individuals.Replacement of the aortic valve using existing catheterizationtechniques is also challenging because it is difficult to anchor aprosthetic valve within a soft and dilated annulus. More particularly,when a prosthetic valve is delivered to the site of the aortic valve andexpanded, it engages and continuously exerts an outward force againstthe aortic valve wall. This continuous outward pressure is necessary foranchoring the prosthetic valve within the native valve but may alsocause the already-dilated native aortic annulus to become furtherexpanded. The tissue along the annulus of a valve suffering from aorticinsufficiency is typically soft and flexible (as opposed to being hardand calcified as with aortic stenosis) and therefore the furtherexpansion of the aortic annulus may lead to dislodgement of theprosthetic valve. Such dislodgement could require delivery of a stilllarger valve or result in death of the patient. A prosthetic valve witha very large diameter may be delivered via a catheterization techniqueto reduce the possibility of dislodgement. However, it follows that sucha valve would also have a large diameter in its crimped condition. Thedelivery of such a large-diameter prosthetic valve is much morechallenging and dangerous than the delivery of a relatively smallprosthetic valve of the type currently used to treat aortic stenosis.

Therefore, a need exists for new and improved methods and devices fortreating aortic insufficiency.

SUMMARY

Embodiments of the disclosed technology are directed to percutaneous(e.g., catheter-based) and/or minimally invasive surgical (MIS)procedures for treating aortic insufficiency. These less invasivetherapies, which do not require open-heart surgery, provide patientswith a more attractive option for early treatment of aorticinsufficiency, thus mitigating or even avoiding the risk of damage tothe left ventricle. These less invasive therapies also provide anurgently needed treatment option for patients who cannot be treated byopen-heart surgery because they are too sick or frail to withstand thetreatment. Unfortunately, at the present time, these “high-risk”patients are typically left untreated.

According to one exemplary embodiment disclosed herein, a system isprovided for replacing the native aortic valve using a catheter-basedapproach. The system includes a transcatheter heart valve (THV),sometimes referred to herein as a “bioprosthesis.” The transcatheterheart valve of this embodiment comprises a support structure, such as astent, formed of, for example, a shape-memory material. The supportstructure can be configured to be radially compressible into acompressed state, expandable into an over-expanded state having a firstdiameter, and self-adjustable into a functional state having a seconddiameter less than the first diameter. The transcatheter heart valve canalso include a flexible valve member or membrane, such as a prostheticone-way valve member, within an interior of the support structure. Inparticular implementations, one or more grabbing mechanisms such asmicro-anchors, are disposed on an outer surface of the supportstructure, where the grabbing mechanisms can be configured to penetrateor otherwise securably engage the support structure to surroundingnative tissue, such as along a valve orifice when the support structureis expanded within the valve orifice.

In particular implementations, at least one of the one or more grabbingmechanisms comprises a projection having a hook, a sharpened barb,tree-shaped barbs, or an anchor-shaped barb. In some embodiments, atleast one of the one or more grabbing mechanisms comprises a strip ofprojections disposed circumferentially around the support structure. Inother implementations, at least one of the one or more grabbingmechanisms comprises a strip of projections disposed along a verticalaxis of the support structure. At least one of the one or more grabbingmechanisms can include a projection that changes shape after a period oftime. For example, the projection can be initially held in an undeployedstate by a resorbable material.

The support structure, the one or more grabbing mechanisms, or both thesupport structure and the one or more grabbing mechanisms can be formedof a shape memory alloy, such as of Nickel-Titanium (Nitinol), in someembodiments. The support structure can be constructed with sufficientradial strength to maintain the native aortic valve in a dilatedcondition such that the prosthetic valve member can effectively replacethe function of the native aortic valve, but is configured such that itsdiameter is not substantially greater than the native valve's diameter.

The flexible membrane can be a valve assembly having an inlet side andan outlet side, the valve assembly being configured to allow flow fromthe inlet side to the outlet side but prevent flow from the outlet sideto the inlet side. In some embodiments, the flexible membrane isconfigured to replace an aortic valve.

Embodiments of a prosthetic heart valve can comprise an inner and outersupport structure that can be delivered separately from one another. Forexample, one embodiment comprises an outer support structure configuredto be radially compressible, expandable into an over-expanded statehaving a first diameter, and self-adjustable into a functional statehaving a second diameter less than the first diameter. The prostheticheart valve can also comprise one or more grabbing mechanisms disposedon an outer surface of the outer support structure, the one or moregrabbing mechanisms being configured to penetrate or otherwise securablyengage the outer support structure to surrounding native tissue, and aninner support structure configured to be radially compressible andexpandable into an expanded state within the interior of the outersupport structure, where a flexible valve member can be secured withinan interior of the inner support structure.

As with other embodiments, embodiments comprising an inner and outersupport structure can also include at least one grabbing mechanism thatcomprises a projection having a hook, a sharpened barb, tree-shapedbarbs, or an anchor-shaped barb. One or more of the outer supportstructure, the inner support structure, or the one or more grabbingmechanisms can be formed of a shape memory alloy. The flexible membranecan be configured to replace an aortic valve. The inner supportstructure can be configured to securably engage the interior of theouter support structure upon being expanded within the outer supportstructure.

In one exemplary method disclosed herein, the transcatheter heart valvecan be “over-expanded” within a native aortic valve using a ballooncatheter. More particularly, an expandable prosthetic heart valve can bepositioned within a patient's aortic valve and expanded, such as byinflating a balloon of a balloon catheter around which the prostheticheart valve is disposed, to an over-expanded diameter thereby causingone or more projections on an outer surface of the prosthetic heartvalve to engage native tissue of the patient's aortic valve. Theprosthetic heart valve can be allowed to retract toward a recoildiameter less than the over-expanded diameter (e.g., a “memorized” (ifthe support structure comprises a shape-memory alloy) or “recoil”diameter), such as by deflating the balloon. As the prosthetic heartvalve recoils (reduces in diameter), the one or more projections areengaged with the native tissue of the patient's aortic valve, therebyreducing a diameter of the patient's native aortic valve. This can occurbecause the projections (e.g. micro-anchors) on the support structureare securely engaged with the tissue of the valve annulus. Conventionalvalves cannot undergo such over-expansion due to materials used andmethods of manufacture.

In some embodiments, the expandable prosthetic heart valve comprises asupport structure made of a shape memory alloy that causes the supportstructure to have the recoil diameter when the support structure is notacted on by any external force. In certain embodiments, the one or moreprojections include hooks, barbs, or anchors. At least one of the one ormore projections changes its shape after penetrating the native tissueof the patient's aortic valve in some embodiments.

This exemplary method of implanting an over-expanded transcatheter heartvalve has a number of advantageous features over known transcatheterheart valves. For example, unlike existing transcatheter heart valves,the over-expanded transcatheter heart valve does not apply an outwardradial force on the native valve annulus after implantation. This isadvantageous because, as discussed above, a regurgitating valvetypically results from a diseased or aging valve annulus that is alreadysubstantially dilated. The application of a continuous outward radialforce on a weakened and dilated annulus will usually dilate the annulusfurther. This could result in serious damage to the anatomical structureof the heart and, as the weakened aortic root dilates further, couldeventually lead to dislodgement of the transcatheter heart valve.

By reducing the diameter of the surrounding annulus, it is also possibleto replace the native aortic valve using a smaller transcatheter heartvalve than would be typically required to treat aortic insufficiency.Due to the recoil of the support structure, the final diameter of theover-expanded transcatheter heart valve is substantially smaller than aconventional THV. A conventional THV must be expanded to a diameter thatis capable of being securely maintained in a dilated valve annulus,whereas the over-expanded transcatheter heart valve constricts theannulus and therefore can have a smaller outer diameter. As a result ofthe smaller final diameter, the over-expanded transcatheter heart valvecan also employ a smaller valve member. The smaller valve member allowsthe over-expanded transcatheter heart valve to be crimped to a muchsmaller diameter and have a smaller profile during advancement throughthe patient's vasculature. It will be recognized by those skilled in theart that a smaller diameter facilitates advancement of the transcatheterheart valve through a patient's vasculature.

Some methods for treating aortic insufficiency can comprise a two-stagedelivery. For example, one method comprises positioning an outer stentwithin a patient's aortic valve, expanding the outer stent to anover-expanded diameter, thereby causing projections on the outer surfaceof the outer stent to engage tissue of the patient's aortic valve,allowing the outer stent to retract toward a recoil diameter that isless than the over-expanded diameter while the projections are engagedwith the tissue of the patient's aortic valve, thereby causing thediameter of the patient's native aortic valve to be reduced, positioninga prosthetic heart valve within the outer stent, and expanding theprosthetic heart valve while the prosthetic heart valve is positionedwithin the outer stent.

In some embodiments, the act of expanding the prosthetic heart valvecomprises frictionally securing the prosthetic heart valve within theouter stent, engaging grooves provided within the outer stent withcomplementary members of the prosthetic heart valve, or engaging a snapmechanism that causes the prosthetic heart valve to be secured withinthe outer stent, and/or inflating a balloon of a balloon catheter aroundwhich the outer stent is disposed. In certain embodiments, the act ofallowing the outer stent to retract comprises deflating the balloon ofthe balloon catheter. In some methods, the outer stent comprises a shapememory alloy. In some methods, the prosthetic heart valve comprises acompressible and expandable inner support structure and a valve membranesecured in an interior of the inner support structure

The foregoing and other features and advantages of the invention willbecome more apparent from the following detailed description, whichproceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an anatomic anterior view of a human heart, with portionsbroken away and in section to view the interior heart chambers andadjacent structures.

FIG. 2 is a perspective view of a transcatheter heart valve formed witha shape-memory stent in accordance with an embodiment of the disclosedtechnology.

FIG. 3 is a perspective view of another embodiment of a transcatheterheart valve formed with a shape memory support structure according tothe disclosed technology.

FIG. 4 shows an elevation view of one embodiment of a projection (ormicro-anchor) that can be used with embodiments of a transcatheter heartvalve.

FIG. 5 illustrates an elevation view of another embodiment of aprojection (or micro-anchor) that can be used with a transcatheter heartvalve.

FIG. 6 illustrates an elevation view of another embodiment of aprojection (or micro-anchor) that can be used with a transcatheter heartvalve.

FIG. 7 illustrates an elevation view of another embodiment of aprojection (or micro-anchor) that can be used with a transcatheter heartvalve.

FIG. 8 illustrates an elevation view of another embodiment of aprojection (or micro-anchor) that can be used with a transcatheter heartvalve.

FIG. 9 illustrates an elevation view of another embodiment of aprojection (or micro-anchor) that can be used with a transcatheter heartvalve.

FIG. 10 is a perspective view of a transcatheter heart valve formed witha shape memory support structure in accordance with another embodimentof the disclosed technology.

FIG. 11 is a simplified side view of a balloon catheter delivery systemthat is configured to over-expand the shape memory support structure ata target area inside a patient's body in accordance with an embodimentof the disclosed technology.

FIGS. 12-15 are simplified sectional views of a transcatheter heartvalve being deployed in accordance with an embodiment of the disclosedtechnology.

FIGS. 16-20 show simplified sectional views of one embodiment of atranscatheter heart valve being deployed in a two-stage processaccording to an exemplary method of the disclosed technology.

FIGS. 21-25 show perspective views of additional embodiments ofprojections (or micro-anchors) that can be used with a transcatheterheart valve.

FIG. 26 is an elevation view of another embodiment of a transcatheterheart valve according to the disclosed technology. In particular, theembodiment illustrated in FIG. 26 has two attachable sections.

DETAILED DESCRIPTION

As used in this application and in the claims, the singular forms “a,”“an,” and “the” include the plural forms unless the context clearlydictates otherwise, Additionally, the term “includes” means “comprises.”Although the operations of exemplary embodiments of the disclosed methodmay be described in a particular, sequential order for convenientpresentation, it should be understood that the disclosed embodiments canencompass an order of operations other than the particular, sequentialorder disclosed. For example, operations described sequentially may insome cases be rearranged or performed concurrently. Further,descriptions and disclosures provided in association with one particularembodiment are not limited to that embodiment, and may be applied to anyembodiment disclosed herein. Moreover, for the sake of simplicity, theattached figures may not show the various ways in which the disclosedsystem, method, and apparatus can be used in combination with othersystems, methods, and apparatuses.

In vertebrate animals, the heart is a hollow muscular organ having fourpumping chambers as seen in FIG. 1. The left and right atria 2, 4 andthe left and right ventricles 6, 8, are each provided with their ownone-way valve. The natural heart valves are identified as the aortic 10,mitral (or bicuspid) 12, tricuspid 14, and pulmonary 16, and are eachmounted in an annulus comprising dense fibrous rings attached eitherdirectly or indirectly to the atrial and ventricular muscle fibers. Eachannulus defines a flow orifice.

The atria 2, 4 are the blood-receiving chambers, which pump blood intothe ventricles 6, 8. The ventricles 6, 8 are the blood-dischargingchambers. The synchronous pumping actions of the left and right sides ofthe heart constitute the cardiac cycle. The cycle begins with a periodof ventricular relaxation, called ventricular diastole. The cycle endswith a period of ventricular contraction, called ventricular systole.The four valves 10, 12, 14, 16 ensure that blood does not flow in thewrong direction during the cardiac cycle; that is, to ensure that theblood does not back flow from the ventricles 6, 8 into the correspondingatria 2, 4, or back flow from the arteries into the correspondingventricles 6, 8. The mitral valve 12 is between the left atrium 2 andthe left ventricle 6, the tricuspid valve 14 between the right atrium 4and the right ventricle 8, the pulmonary valve 16 is at the opening ofthe pulmonary artery, and the aortic valve 10 is at the opening of theaorta. As discussed, in aortic insufficiency, the aortic valve 10 canbecome dilated, thus preventing the valve from fully closing.Embodiments of the present disclosure can be deployed to the aorticvalve, specifically to the area of the aortic valve annulus, to treataortic insufficiency.

FIG. 2 is a perspective view of an exemplary transcatheter heart valve100 (also referred to as bioprosthesis 100). Bioprosthesis 100 includesa tubular support structure 102, a flexible membrane 104 (e.g., a valvemember), a membrane support 106, and one or more grabbing mechanisms 108affixed about a circumference of the support structure 102.

The support structure 102 in FIG. 2 can be formed of a shape memorymaterial, such as Nitinol. In one exemplary embodiment, the supportstructure 102 can be radially compressed into a compressed state fordelivery through the patient's vasculature, but can self expand to anatural, uncompressed or functional state having a preset diameter. Inother words, the support structure 102 moves or tends toward a presetdiameter when free of external forces. Furthermore, the supportstructure 102 can be expanded beyond its natural diameter to anover-expanded diameter. After the support structure 102 is in thisover-expanded state, the support structure returns toward its presetdiameter (or naturally recoils to the preset or recoil diameter).

The support structure 102 can be generally tubular in shape and has alongitudinal flow path along its structural axis. The support structure102 can include a grated framework, such as a stent, configured tosecure bioprosthesis 100 within or adjacent to the defective valveannulus of the heart. The support structure 102 further providesstability and prevents the bioprosthesis 100 from migrating after it hasbeen implanted.

In alternative embodiments, the support structure 102 can comprise othershape memory alloys, or other materials capable of providing sufficientsupport for the bioprosthesis 100. Such materials can include othermetals, metal alloys such as stainless steel or cobalt chromium, and/orpolymers. The support structure 102 can have configurations other thanthat shown in FIG. 2. For example, the support structure 102 can have adifferent shape, more or fewer vertical support bars, and/or additionalstructures for added stability. The support structure 102 can comprise astrut mesh and/or sleeve structure.

The flexible membrane 104 is a valve member that is positionable in theflow path of the support structure 102 and that is configured to permitflow in a first direction but substantially resist flow in a seconddirection. In certain implementations, the flexible membrane 104comprises a biological tissue formed into a valve member. The biologicaltissue which forms the valve member can comprise pericardial tissueharvested from an animal heart, such as porcine, bovine, or equinepericardium. The flexible membrane 104 can also comprise, alternativelyor additionally, biocompatible materials including synthetic polymerssuch as polyglycolic acid, polylactic acid, and polycaprolactone, and/orother materials such as collagen, gelatin, chitin, chitosan, andcombinations thereof.

The membrane support 106 can be positionable in the flow path andaffixed to the support structure 102. Membrane support 106 can comprisepolyethylene terephthalate (PET) (e.g., Dacron), or any other suitablematerial. The membrane support 106 can be positioned such that it foldsunder and around the bottom of the flexible membrane 104. The membranesupport 106 can be sutured or otherwise affixed to the flexible membrane104. In some embodiments, the membrane support 106 can comprise a skirton the exterior surface of the flexible membrane 104, and a thinnerribbon on the interior surface of the flexible membrane 104, within theflow path. In this embodiment, the ribbon and skirt structures of themembrane support 106 can be sutured together, with a portion of theflexible membrane between them. In some embodiments, the membranesupport 106 can be a thin layer of material, such as a layer of PET thatcan be from about 0.01 mm thick to about 0.2 mm thick. In someembodiments, the thickness of the membrane support 106 can vary from thecenter to the edge. For example, in one embodiment, the membrane support106 can be about 0.07 mm thick at an edge, and about 0.05 mm thick atthe center. In another specific embodiment, the membrane support 106 canbe about 0.13 mm thick at the edge, and about 0.10 mm thick at thecenter. Additional details of the support structure 102, the flexiblemembrane 104, and the membrane support 106 are described in U.S. Pat.Nos. 6,730,188 and 6,893,460, both of which are hereby incorporatedherein by reference. Furthermore, U.S. Pat. Nos. 6,730,188 and 6,893,460describe additional prosthetic valve that can be modified according tothe disclosed technology and used as part of any of the disclosedapparatus or systems or used with any of the disclosed methods orprocedures.

In certain embodiments, grabbing mechanisms 108 are configured as stripsof projections or micro-anchors 110. The grabbing mechanisms 108 canvary from implementation to implementation, but in certainimplementations comprise any structure capable of at least partiallypenetrating and engaging the target tissue. For example, the projections110 can be designed to at least partially penetrate and/or otherwiseengage (e.g. by clamping or grabbing) the surrounding tissue uponover-expansion and to contract the aortic annulus and surrounding nativetissue along with the support structure 102 upon recoil of the supportstructure 102. In other embodiments, the projections 110 may includebarbed projections, umbrella projections, and/or hooks also designed toat least partially penetrate the tissue upon over-expansion and contractthe aortic annulus and surrounding tissue upon recoil of the supportstructure 102.

As shown in FIG. 2, the grabbing mechanisms 108 can be positioned andcoupled to the support structure 102 as vertical, or axial, strips ofprojections 110. In an alternative embodiment shown in FIG. 3, thegrabbing mechanisms 109 can be positioned and coupled to the supportstructure 102 as one or more horizontal, or circumferential, strips ofprojections 111. For example, one or more strips of projections 111 canbe disposed around the circumference of the support structure 102. Suchgrabbing mechanisms 109 can extend substantially around thecircumference of the support structure 102, and/or strips of projections111 can extend only partially around the circumference of the supportstructure 102, such as horizontal arcs of projections. In someembodiments, projections can be provided in one or more localized areasof the support structure 102, in addition to or instead of beingprovided in linear strips. In certain embodiments, one or more strips ofprojections can be provided along one or more struts or wires of thesupport structure 102, substantially paralleling the angles of thesupport structure 102. In another embodiment, the strips can be disposedcircumferentially around the support structure 102 and located along thecommissural supports (e.g. portions of the support structure whereinadjacent prosthetic leaflets meet and attach to the support structure)of support structure 102.

Some implementations of the bioprosthesis 100 shown in FIGS. 2 and 3 cancomprise only one grabbing mechanism 108, 109. Alternative embodimentscan comprise two or more grabbing mechanisms 108, 109. Further, thegrabbing mechanisms 108, 109 can be manufactured separately from thesupport structure 102 and attached to the support structure through asuitable means (e.g., sutures, adhesive, weld, snap-fit mechanism,friction, and the like). Alternatively, the grabbing mechanisms 108, 109can be formed as an integral feature of the support structure. Eachgrabbing mechanism 108, 109 generally comprises one or more projectionsor micro-anchors 110, 111. The projections or micro-anchors 110 can haveany suitable dimension. For instance, the projections 110 can have alength from approximately 1 mm to approximately 2 mm. Projections 110can be smaller in some embodiments, such as having a length from about0.001 mm to about 1 mm. Alternatively, projections 110 can be larger insome embodiments, such as having a length from about 2 mm to about 6.5mm or larger. In some embodiments, a grabbing mechanism 108, 109 caninclude a plurality of projections 110, where at least a firstprojection can be a different size from a second projection. A singlegrabbing mechanism can include a plurality of sizes of projections.

In some embodiments, the projections can be formed of a shape memorymaterial that is configured to change shape. For instance, in oneimplementation, the projections can change shape after penetrating thetissue. For example, barbs at the tip of the projections can change inangle or configuration in relation to the projection after penetratingthe tissue in order to more securely engage with the tissue. In anotherembodiment, the projections can change shape after expansion of thesupport structure 102. For example, the projections 110 can lay flatagainst the support structure 102 while the bioprosthesis is in itscontracted configuration, and the projections can expand and the barbscan change shape to extend laterally outward from the projection toprevent the projection from slipping out of the tissue once thebioprosthesis 100 has been expanded.

In one variation, one or more projections can be configured with adelayed release mechanism, such that at least a portion of eachprojection changes shape after a period of time. This may be achieved byincorporating a resorbable material into the projection for temporarilyholding the projection in a constrained condition. As the resorbablematerial is resorbed by the body, the projection becomes free to assumeits relaxed condition. As the projection moves to its relaxed condition,its shape can change to more securely engage and hold the surroundingtissue. For example, barbs or hooks associated with the projection caninitially be held against the main body portion of the projection untilthe resorbable material is resorbed. At that time, the barb or hook canextend outwardly from the main body portion, thereby creating a moresecure attachment to the tissue in which the projection is inserted.

FIGS. 4-9 show elevation views of various embodiments of projections400, 402, 404, 406, 408, 410 that can be used with embodiments of atranscatheter heart valve according to the present disclosure. Ingeneral, the projections 400, 402, 404, 406, 408 include a main bodyportion and one or more barbs. For instance, the illustrated projectionsinclude projection 400 with a single sharpened barb 401, projection 402with a hook-shaped barb 403, projection 404 with an anchor-shaped (arrowhead) barb 405, projection 406 with multiple branch-like barbs 407,projection 408 with multiple tree-shaped sharpened barbs 409, andhook-shaped projection 410. Suitable projections further include spikes,staples, fasteners, tissue connectors, or any other suitable projectioncapable of engaging with a patient's native tissue. Embodiments ofsuitable projections 400, 402, 404, 406, 408, 410 can be designed topenetrate the aortic valve annulus and engage or lodge within thethickness of the aortic valve annulus such that when the bioprosthesisretracts toward its natural state, the projections pull the patient'snative tissue inward towards the center of the flow path, substantiallywithout dislodging from their engaged positions. The barbs can be formedon the projections 400, 402, 404, 406 408 by laser cutting or otherappropriate manufacturing method. Suitable materials for projectionsinclude Nitinol, other shape memory alloys, stainless steel, cobaltchromium, titanium, Elgiloy, HDPE, nylon, PTFE, other biocompatiblepolymers, resorbable materials, and combinations thereof. Other suitablematerials are known in the art, and the projections of the presentdisclosure are not limited to those discussed.

FIGS. 21-25 illustrate additional possible embodiments of projections416, 418, 420, 422, 424. FIG. 21 shows a projection 416 that has asquare cross-sectional base and a pyramidal pointed tip, wherein acutout between the base and the tip can facilitate engagement within apatent's native tissue. FIG. 22 shows a pointed projection 418 that canextend at an angle from the surface of a support structure orbioprosthesis. FIG. 23 shows an asparagus tip-like projection 420. FIG.24 shows a conical projection 422. FIG. 25 shows another embodiment of atree-like projection 424.

FIG. 10 is a perspective view of another embodiment of a transcatheterheart valve 100 a (also referred to as bioprosthesis 100 a) according tothe disclosed technology. Bioprosthesis 100 a includes a supportstructure 102 a having a tubular or cylindrical base, a flexiblemembrane 104 a (e.g., valve member), a membrane support 106 a and atleast one grabbing mechanism 108 a affixed about a circumference of thesupport structure 102 a. The support structure 102 a is expandable froma first reduced diameter to a second enlarged diameter, and has a flowpath along a structural axis. The support structure 102 a generally caninclude a tubular framework, such as a stent, which primarily securesbioprosthesis 100 a within or adjacent to the defective valve annulus ofthe heart. In this embodiment, the support structure 102 a is configuredto approximate the shape of the flexible membrane 104 a such that theupper end of support structure 102 a comprises peaks at the commissuresupports and valleys (e.g. U-shaped cusps) between the commissuresupports.

FIG. 26 is a perspective view of another embodiment of a transcatheterheart valve having two attachable sections 700, 702 that can bedelivered separately. This embodiment can reduce the cross-sectionalprofile during delivery because each section 700, 702 can have a smallerdelivery profile than the entire assembled bioprosthesis. In theillustrated embodiment, outer section 700 comprises an outer stentstructure 710, and inner section 702 comprises an inner stent structure720 and a valve member 722. In this embodiment, the inner stentstructure 720 and the valve member 722 together form the expandableprosthetic heart valve. The outer section 700 can optionally include atemporary valve member 712, which can be thinner or less durable thanthe more permanent valve member 722. The temporary valve member 712 canbe mounted on or otherwise secured to the outer stent structure 710using any suitable mechanism (e.g., sutures, snaps, screws, friction,hooks, barbs, adhesives, and/or a slide structure). Furthermore, thetemporary valve member 712 can be configured to have a diameter andflexibility suitable to receive the inner section 702 during valvedelivery. The valve member 722 can be any valve as described herein andcan be mounted to or otherwise secured to the inner stent structure 720using any suitable means (e.g., sutures, snaps, screws, a slidestructure, friction, hooks, barbs, and/or an adhesive).

In some embodiments, the outer section 700 can comprise a thincompressible member 712 that can facilitate securing the inner section702 within the outer section 700. Such a compressible member 712 cancreate a tight seal between the outer section 700 and the inner section702 as the inner section presses into the compressible material. Furtherdetails regarding a compressible member 712 are disclosed in U.S. PatentApplication Publication No. 2008/0208327, which is hereby incorporatedherein by reference.

According to one exemplary delivery procedure, and as more fullyexplained below in connection with FIGS. 16-20, the outer section 700 isdelivered to the aortic valve first. The outer stent structure 710, likeembodiments discussed above, can comprise a shape memory alloy such asNitinol, and can have a predetermined recoil (or natural) diameter. Theouter section 700 can be over-expanded to a diameter greater than itsrecoil diameter. For example, the outer section 700 can be disposedaround a balloon catheter and delivered to the interior of the nativeheart valve. The balloon of the balloon catheter can then be inflated,causing the outer section 700 to expand to a diameter beyond its recoildiameter. In particular implementations, the outer section 700 comprisesone or more grabbing mechanisms 708 configured to engage with the nativetissue when the outer stent structure 710 is over-expanded. For example,the grabbing mechanisms 708 can be any of the grabbing mechanismsdescribed above. Once the balloon of the balloon catheter is deflatedand removed, the outer section 700 will contract to its memorized orrecoil diameter. On account of the engagement of the grabbing mechanisms708 to the surrounding tissue, the contraction of the outer section 700will cause the size of the aortic annulus to be reduced as well. Innersection 702 can then be delivered and engaged with the outer section700.

In an alternative method of delivering the two part bioprosthesis, theouter section 700 can be delivered to the interior of a native heartvalve in a crimped state, and allowed to expand to its predeterminednatural diameter, once positioned. A balloon can then be inserted withinthe outer section 700. When the balloon is expanded, the outer sectioncan be over-expanded to a diameter greater than its natural diameter toallow the grabbing mechanisms of the outer section 700 to engage withthe native valve tissue. When the balloon is deflated, contraction ofthe outer section 700 can cause the size of the aortic annulus to bereduced. When compared to the previous method, this can allow fordelivering the outer section 700 in a smaller crimped state, because theouter section 700 is not crimped over the balloon for delivery; theballoon is not inserted until after the outer section 700 is firstallowed to expand to its natural diameter. Inner section 702 can then bedelivered and engaged with the outer section 700.

FIG. 11 is a simplified illustration of a balloon catheter 200, whichcan be used to deliver and deploy a bioprosthesis (such as bioprosthesis100 shown in FIG. 2 above) into a native heart valve. In one embodiment,the balloon catheter 200 advances the bioprosthesis 100 through an outersheath of the delivery system over a guide wire 204. The ballooncatheter 200 can also be configured to aid in the delivery andpositioning of the bioprosthesis 100 within the native valve. Forexample, as shown in FIG. 11, the balloon catheter 200 can include atapered nose cone tip 206 at its distal end that allows a balloonportion 202 and bioprosthesis 100 to cross easily into the native valve.The balloon portion 202 can be inflated (e.g., using a controlled volumeof saline), causing the bioprosthesis 100 to expand within and engagethe native hart valve.

In one exemplary method, the guide wire 204 is inserted into the femoralartery of a patient, advanced through the aortic arch of a patient, andinto the aortic valve. The balloon catheter 202 is advanced through theouter sheath of the delivery system, over the guide wire 204, and intothe aortic valve. The bioprosthesis 100 is then positioned and securedwithin the native valve by inflating the balloon portion 202. FIGS.12-15, described below, illustrate one exemplary procedure for deployingthe bioprosthesis 100 into the native valve. The balloon portion 202 canthen be deflated, and the balloon catheter 202 retracted from thepatient's aorta and femoral artery. An exemplary delivery systemdesigned to deliver the bioprosthesis 100 is the RETROFLEX II catheterassembly available from Edwards Lifesciences in Irvine, Calif.Furthermore, although the operation described above is a percutaneoustransfemoral procedure, it should be understood that embodiments of thedisclosed technology include the use of a shorter catheter assembly orsemi-rigid cannula for deploying a bioprosthesis in a minimally invasivesurgical (MIS) procedure, such as a trans-apical procedure. In atransapical procedure, the catheter or cannula is inserted through a gapbetween the ribs and is advanced through a small incision formed alongthe apex of the heart. This technique advantageously provides thesurgeon with a direct line of access to the aortic valve. U.S. PatentApplication Publication Nos. 2008/0065011, 2007/0005131, and 2007/008843disclose further details regarding suitable delivery methods, and arehereby incorporated herein by reference.

FIGS. 12-15 are schematic cross-sectional views of a patient's aortaillustrating delivery of the support structure and valve of FIG. 2. Asshown in FIG. 12, in one embodiment, the bioprosthesis 100 may beintroduced into the patient's body using a percutaneous deliverytechnique with the balloon portion 202 of the balloon catheter 200deflated, and the bioprosthesis 100 operably disposed thereon. Thebioprosthesis can be contained in a radially crimped or compressedstate. In embodiments using a self-expandable bioprosthesis 100, thebioprosthesis 100 can be held in a compressed state for delivery, by,for example, containing the bioprosthesis within an outer covering orsheath 201. The outer covering 201 can be removed or retracted, or thebioprosthesis 100 pushed through the outer covering 201, to allow theself-expandable bioprosthesis 100 to self-expand. In embodiments havinga bioprosthesis that does not self-expand, such an outer covering maynot be needed to retain the bioprosthesis in a crimped state, but cannonetheless be used if desired (e.g. to reduce friction duringdelivery).

In the embodiment illustrated in FIG. 12, the projections 110 of thegrabbing mechanisms 108 are disposed around the outside circumference ofsupport structure 102.

In the illustrated embodiment the bioprosthesis 100 is introduced andpositioned across the native aortic valve annulus (AVA) 300 by beinginserted at least partially through native valve leaflets 302 andexpanded. Because the AVA of an aortic valve suffering from aorticinsufficiency is dilated, diameter D1 of the AVA 300 is expected to belarger than the diameter of a healthy AVA.

As shown in FIG. 13, outer sheath or covering 201 can be retracted orremoved from over the bioprosthesis 100. In embodiments having abioprosthesis 100 comprising a shape memory alloy, the bioprosthesis canexpand from its crimped or compressed diameter d to a predetermined ormemorized diameter R once the sheath 201 is removed.

As shown in FIG. 14, the balloon portion 202 of the balloon catheter 200is expanded to increase the diameter of the support structure 102 fromits relaxed diameter R (FIG. 13) to an over-expanded diameter OE suchthat the outer diameter of the bioprosthesis 100 equals or exceeds theoriginal diameter D1 of the AVA 300. In this manner, the AVA 300 mayexpand beyond the diameter D1 as well. During the expansion, theprojections 110 of the grabbing mechanisms 108 are forced to contact andcan penetrate or otherwise engage (e.g. clamp or grab) the targettissue, which may include the AVA 300 and some of the tissue surroundingthe AVA. This causes the bioprosthesis 100 to adhere to the surroundingtissue.

Next, as shown in FIG. 15, the balloon portion 202 of the ballooncatheter 200 can be deflated, and the balloon catheter 200 removed fromthe AVA 300. In embodiments where the support structure 102 is formed ofa shape memory material, removing the expansion force of balloon 202from support structure 102 allows the support structure 102 to returnfrom an over-expanded diameter OE (FIG. 14) to a recoil or relaxeddiameter R. The manufacture of the support structure (i.e., stent)determines what the recoil diameter will be. For example, the recoildiameter of a support structure comprising a shape memory alloy can bethe memorized or functional diameter of the support structure. Therecoil diameter of a support structure comprising, for example,stainless steel and/or cobalt chromium can be that of the natural orresting diameter of the support structure, once it inherently recoilsfrom being over-expanded by the balloon 202. As the diameter ofbioprosthesis 100 decreases to the recoil diameter R, the diameter ofthe AVA 300 also decreases to a final diameter D2. The AVA 300 candecrease in diameter due to the projections 110 of the support structure102 pulling the target tissue inward.

An existing bioprosthesis is generally configured to be radiallyexpanded to a diameter capable of providing secure fixation in a dilatedAVA. However, as discussed above, existing bioprostheses are not wellsuited for treating aortic insufficiency due to the lack of firm tissuein the aortic annulus. Using existing technology, a larger bioprosthesiscould be used to create a more secure fixation; however, a largerbioprosthesis cannot be easily crimped down for delivery via acatheterization technique. In contrast, embodiments of the presentbioprosthesis 100 allow for the collapsed diameter of bioprosthesis 100to be a smaller diameter because bioprosthesis 100 may be assembled witha smaller stent and a smaller valve member. This smaller size ispossible because, rather than stretch the AVA, the present bioprosthesisadvantageously reduces the diameter of the AVA during implantation. As aresult, a smaller overall structure can be achieved which allows thesupport structure 102 of bioprosthesis 100 to be crimped to the smallercollapsed diameter and thus have a smaller profile for delivery througha patient's vasculature. For example, in some embodiments, bioprosthesis100 can be crimped to a size of from about 4 French to about 7 French.

In alternative embodiments, the bioprosthesis 100 need not be operablydisposed on the balloon 202 during delivery. For example, thebioprosthesis 100 can be crimped onto the catheter 200 at a differentlocation than the balloon 202. The bioprosthesis can be allowed toself-expand once positioned within a patient's native aortic valve, andthe balloon 202 can be positioned inside the self-expanded bioprosthesis100 and inflated to then over-expand the bioprosthesis 100.

FIGS. 16-20 show simplified elevation views of one embodiment of atranscatheter heart valve being deployed in a two-stage processaccording to one method of the present disclosure. The illustratedmethod can be used, for example, to deliver the transcatheter heartvalve assembly shown in FIG. 11. In the method illustrated in FIGS.16-20, the outer section 700 can be deployed to the aortic valveseparately from valve member 702. FIG. 16 shows the outer section 700 ona balloon 202, positioned inside the leaflets 302 of the aortic valveannulus 300. The outer section 700 can be a self-expanding stent, suchas a stent comprising a shape memory alloy, or the outer section 700 canbe simply balloon expandable, such as a stent comprising stainlesssteel, cobalt chromium and/or other suitable biocompatible materials.FIG. 17 shows the balloon 202 in an inflated configuration, which canexpand the outer section 700 such that grabbing mechanisms 708 engagewith the native tissue of the leaflets 302 and/or the aortic valveannulus 300.

As shown in FIG. 18, the balloon 202 can be deflated and removed. Theouter section 700 can reduce the diameter of the aortic valve annulus300 as it retracts after the balloon 202 is removed. The outer section700 can retract to a functional or memorized diameter if it comprises ashape memory alloy, or the outer section 700 can simply naturally recoilor retract due to the ductility of the material. The inner section 702can be positioned within the outer section 700 using a catheter 200 anda balloon 202, as shown in FIG. 19. As shown in FIG. 20, the balloon 202can be expanded, thus expanding the crimped inner section 702, allowingit to engage with the outer section 700.

The outer section 700 and the inner section 702 can be delivered on asingle catheter 200 or on separate catheters. For example, a catheter200 can include two expandable balloons, one distal to the other. Afirst balloon can be used to expand the outer section 700 then deflatedand either guided through the lumen of the expanded outer section 700 orremoved back through the lumen. The second balloon and inner section 702can then be positioned within the outer section 700, and the secondballoon can be expanded, allowing for the inner section 702 to engagewith the outer section 700. The second balloon can then be deflated, andthe catheter 200 removed, thus removing the first and second balloons.In alternative embodiments, separate catheters can be used, such that afirst catheter is used to deliver a first balloon and the outer section700 to the native valve, and a second catheter is used to deliver asecond balloon and the inner section 702 to the native valve once theouter section has been deployed and the first catheter has been removed.

While FIG. 16 illustrates the outer section 700 being delivered whilealready crimped on the balloon 202, in alternative embodiments, theouter section 700 can be located at a different position on the catheter200 than the balloon 202. For example, in some embodiments, a crimpedouter section 700 can be delivered to a native aortic valve and allowedto self-expand, such as by removing an outer covering. The balloon 202can then be positioned within the expanded outer section 700 andinflated, thereby over-expanding the outer section 700, allowing thegrabbing mechanisms 708 to engage with the native tissue. The ballooncan then be deflated and removed, and the inner section 702 can bedelivered and engaged with the outer section 700.

It should be understood that embodiments of bioprosthesis 100 can bedeployed using a non-inflatable, mechanical embodiment of deliverycatheter 200. Furthermore, bioprosthesis 100 can be delivered using anysuitable delivery method, including both transapical and femoral arterydelivery methods. Additionally, although the disclosed embodimentsconcern aortic valve replacement, embodiments of the disclosedtechnology can be used to replace any dilated heart valve (e.g., adilated mitral valve). Moreover, although bioprosthesis 100 is used asan exemplary embodiment of the disclosed technology, it should beunderstood that bioprosthesis 100 and bioprosthesis 100 a may beconsidered interchangeable with one other, or with any otherbioprosthesis made or adapted in accordance with the teachings of thedisclosed technology.

Having illustrated and described the principles of the disclosedtechnology, it will be apparent to those skilled in the art that thedisclosed embodiments can be modified in arrangement and detail withoutdeparting from such principles. In view of the many possible embodimentsto which the principles of the disclosed technologies can be applied, itshould be recognized that the illustrated embodiments are only preferredexamples of the technologies and should not be taken as limiting thescope of the invention. Rather, the scope of the invention is defined bythe following claims and their equivalents. I therefore claim all thatcomes within the scope and spirit of these claims.

1. A prosthetic heart valve comprising: a support structure configured to be radially compressible into a compressed state, expandable into an over-expanded state having a first diameter, and self-adjustable into a functional state having a second diameter less than the first diameter; a flexible valve member secured within an interior of the support structure; and one or more grabbing mechanisms disposed on an outer surface of the support structure, the one or more grabbing mechanisms being configured to penetrate or otherwise securably engage the support structure to surrounding native tissue.
 2. The prosthetic heart valve of claim 1, wherein at least one of the one or more grabbing mechanisms comprises a projection having a hook, a sharpened barb, tree-shaped barbs, or an anchor-shaped barb.
 3. The prosthetic heart valve of claim 1, wherein the support structure, the one or more grabbing mechanisms, or both the support structure and the one or more grabbing mechanisms are formed of a shape memory alloy.
 4. The prosthetic heart valve of claim 1, wherein the flexible membrane is a valve assembly having an inlet side and an outlet side, the valve assembly being configured to allow flow from the inlet side to the outlet side but prevent flow from the outlet side to the inlet side.
 5. The prosthetic heart valve of claim 1, wherein the flexible membrane is configured to replace an aortic valve.
 6. The prosthetic heart valve of claim 1, wherein at least one of the one or more grabbing mechanisms comprises a strip of projections disposed eircumferentially around the support structure.
 7. The prosthetic heart valve of claim 1, wherein at least one of the one or more grabbing mechanisms comprises a strip of projections disposed along a vertical axis of the support structure.
 8. The prosthetic heart valve of claim 1, wherein at least one of the one or more grabbing mechanisms includes a projection that changes shape after a period of time.
 9. The prosthetic heart valve of claim 8, wherein the projection is initially held in an undeployed state by a resorbable material.
 10. A prosthetic heart valve comprising: an outer support structure configured to be radially compressible, expandable into an over-expanded state having a first diameter, and self-adjustable into a functional state having a second diameter less than the first diameter; one or more grabbing mechanisms disposed on an outer surface of the outer support structure, the one or more grabbing mechanisms being configured to penetrate or otherwise securably engage the outer support structure to surrounding native tissue; an inner support structure configured to be radially compressible and expandable into an expanded state within the interior of the outer support structure; and a flexible valve member secured within an interior of the inner support structure.
 11. The prosthetic heart valve of claim 10, wherein at least one of the one or more grabbing mechanisms comprises a projection having a hook, a sharpened barb, tree-shaped barbs, or an anchor-shaped barb.
 12. The prosthetic heart valve of claim 10, wherein any one or more of the outer support structure, the inner support structure, or the one or more grabbing mechanisms are formed of a shape memory alloy.
 13. The prosthetic heart valve of claim 10, wherein the flexible membrane is configured to replace an aortic valve.
 14. The prosthetic heart valve of claim 10, wherein the inner support structure is configured to securably engage the interior of the outer support structure upon being expanded within the outer support structure.
 15. A method, comprising: positioning an expandable prosthetic heart valve within a patient's aortic valve; expanding the prosthetic heart valve to an over-expanded diameter, thereby causing one or more projections on an outer surface of the prosthetic heart valve to engage native tissue of the patient's aortic valve; and allowing the prosthetic heart valve to retract toward a recoil diameter less than the over-expanded diameter as the one or more projections are engaged with the native tissue of the patient's aortic valve, thereby reducing a diameter of the patient's native aortic valve.
 16. The method of claim 15, wherein the act of expanding the prosthetic heart valve comprises inflating a balloon of a balloon catheter around which the prosthetic heart valve is disposed.
 17. The method of claim 16, wherein the act of allowing the prosthetic heart valve to retract comprises deflating the balloon of the balloon catheter.
 18. The method of claim 15, wherein the expandable prosthetic heart valve comprises a support structure made of a shape memory alloy that causes the support structure to have the recoil diameter when the support structure is not acted on by any external force.
 19. The method of claim 15, wherein the one or more projections include hooks, barbs, or anchors.
 20. The method of claim 15, wherein at least one of the one or more projections changes its shape after penetrating the native tissue of the patient's aortic valve.
 21. A method, comprising: positioning an outer stent within a patient's aortic valve; expanding the outer stent to an over-expanded diameter, thereby causing projections on the outer surface of the outer stent to engage tissue of the patient's aortic valve; allowing the outer stent to retract toward a recoil diameter that is less than the over-expanded diameter while the projections are engaged with the tissue of the patient's aortic valve, thereby causing the diameter of the patient's native aortic valve to be reduced; positioning a prosthetic heart valve within the outer stent; and expanding the prosthetic heart valve while the prosthetic heart valve is positioned within the outer stent.
 22. The method of claim 21, wherein the act of expanding the prosthetic heart valve comprises frictionally securing the prosthetic heart valve within the outer stent.
 23. The method of claim 21, wherein the act of expanding the prosthetic heart valve comprises engaging grooves provided within the outer stent with complementary members of the prosthetic heart valve.
 24. The method of claim 21, wherein the act of expanding the prosthetic heart valve comprises engaging a snap mechanism that causes the prosthetic heart valve to be secured within the outer stent.
 25. The method of claim 21, wherein the act of expanding the outer stent comprises inflating a balloon of a balloon catheter around which the outer stent is disposed.
 26. The method of claim 25, wherein the act of allowing the outer stent to retract comprises deflating the balloon of the balloon catheter.
 27. The method of claim 21, wherein the outer stent comprises a shape memory alloy.
 28. The method of claim 21, wherein the prosthetic heart valve comprises a compressible and expandable inner support structure and a valve membrane secured in an interior of the inner support structure. 